Hello guys!!!First build I ever make so be gentle when commenting...
Olaf is my main and I really wanted to add to mobafire's builds one more olaf build.Also,if you have anything to suggest I am glad to hear...
IMPORTANT!!!
This build is good in both maps but really shines in 3 vs 3

pros:
HEAVY DAMAGE
1)looks damn COOL
2)easy stealer(a lot of auto attack damage,q every 2 secs,e,A LOT OF CRIT)
3)one of the best ulties ever(in my opinion)
cons:
1)not this tanky with my build(NEVER dive first,dive at the same time others do too)
2)q needs skill to throw
3)too many bottons to press to start your combo(considering youmuu's too we have a total of 4 bottons,excluding your q)

OK this is what I use:
For marks ALWAYS get arm pen,as it is pretty simple:you must take them down and with no armor you will faster than usual
For seals my favourites are dodge,when you dive you need to stay alive,so dodge is even better than armor runes
For glyphs I use the flat cdr.Throw that axe baby!!!
quintessenses is where I am still testing.Though 3 as is good,I find better having 3 dodge.More dodge,more miracle kills

for masteries look above I am too bored to write here(sorry for my attitude I just broken up).
21-0-9 rules(21-9-0 is good too,but lacks mana regen)

Exhaust and Ghost.Nothing else to add.
Ignite is good too but you need that ghost.Flash can be taken instead of exhaust.ghost is needed more.Anything else is useless(don't try to argue about that it is true)

Now for the funny part.Many argue about which is better to focus on:q or e?The answer:Q man...
Very obvious.An axe flying every 2 secs is better than a drunk viking attacking head on and killing himself(I exaggerated a bit I guess).The point is that if you skill e more than q you will get stolen,lose the gold and lose the game,as you will not be able to make the VERY expensive items you have on your mind.Q is a massive stealing move,slow,heavy damage with your arm pen.Nothing else.Then max second your w,none will dare come in range for attack.E is a good skill but keep it for scaring your opponents(look kinda scary when used hehehe).ulti when possible

ok now for the best part of every build.
ITEMS
start with the doran blade for some extra damage,lifesteal and survivability.
Next up you make berzerker's greaves.Olaf is a berzerker,so nothing else fits better(you can change them for ninja tabi but I dn't recommend it)
The next item is a MUST.The brutalizer has all that olaf needs:damage,arm pen AND cdr.Also,you can use this to make your first stample item,youmuu's ghostblade.This one is the miracle item of the build.It gives out crit,damage,arm pen,cdr and when used movement to close the gap between you and your opponents as well as massive AS for 8 seconds.What does this mean?ULTI,GHOST,YOUMUU'S,W AND YOU GOT A TRIPLE KILL(if you possitioned correctly before the gank).After you get fed you have to keep building damage so that none will be more than 5 hits to kill.The bloodthirster is the perfect item:the item giving the most damage in the game and also great lifesteal bonus to make your deadly ulti,ghost,youmuu's,w even deadlier.By the time you make bloodthirster the game is won(3 vs 3).Even if your opponents keep playing,force them to surrender with frosen mallet,the only thing that could result in your death was your low survivability,that one is gone too!!!Build one infinity edge to make them cry(OP FED,OP FED).The game should end the moment you built your frosen,but if it is STILL on finish it with phantom dancer and after they die write in chat:BRO BRO!!!NONE ESCAPES A DRUNK VIKING!!

For the extra session I would like to tell you a bit of things you may already know but let's see.THE MUST THING YOU NEED TO KNOW is w can be used to take down towers(wow what a great discovery I did lol).Next up,when you have your bloodthirster and youmuu's all creeps will die with an axe(not the super and the big ones).Q REVEALS the area the axe is thrown(for 0,25 secs).When the crutial time for your deadly combo comes,dive in by throwing your axe,then ghost,ulti,yoummu's and last w(all these should have half a second delay after the previous one).This way you will do as much damage as possible for a longer time(about 2 more secs with youmuu's=4 attacks,1/2 sec more ulti,ghost doesn't matter it is long enough alone and 1 more sec w=2 attacks)Last but not least,try to jungle the buffs as long as they spawn(in 5 vs 5 always get the enemie's blue buff if your team needs yours)

That's all.Rate and comment I hope I added one new champ to your mains hehe